Arrays of relatively small structures, sometimes referred to as microneedles or micro-pins, have been disclosed for use in connection with the delivery and/or removal of therapeutic agents and other substances through the skin and other surfaces.
The vast majority of known microneedle devices include structures having a capillary or passageway formed through the needle. Because the needles are themselves small, the passageways formed in the needles must be limited in size. As a result, the passageways can be difficult to manufacture because of their small size and the need for accurate location of the passageways within the needles. Another potential problem of passageways small enough to fit within the microneedles is that the passageways may become easily obstructed or clogged during use.
As a result, a need existed for microneedle devices that include fluid passageways that are easier to manufacture and that are resistant to obstruction or clogging during use. This need was answered in part by copending and commonly assigned U.S. patent application Ser. No. 09/947,195, filed on Sep. 5, 2001 and entitled MICRONEEDLE ARRAYS AND METHODS OF MANUFACTURING THE SAME. The microneedles disclosed in that application include channels formed in their outer surfaces, with the channels extending from the base towards the tip of each microneedle. The channels provide convenient fluid paths in connection with the microneedles. The microneedle arrays disclosed in that application may also include conduit structures formed on the substrate surface to enhance fluid flow across the surface of the substrate from which the microneedles project. Once the microneedles have penetrated the skin, a sample of body fluid may flow through the channels to be collected by the conduit structure towards, for example, some type of sensor. Although the conduit structures can facilitate fluid transport in connection with the microneedles, improvements may still be possible with regard to transporting fluid quickly and efficiently across the devices to, e.g., sensors, etc.